looking for some old RAM chips

From: Ross Archer <dogbert_at_mindless.com>
Date: Wed Apr 18 03:03:35 2001

----- Original Message -----
From: <Demon02554_at_aol.com>
To: <classiccmp_at_classiccmp.org>
Sent: Tuesday, April 17, 2001 6:11 PM
Subject: looking for some old RAM chips


> ok...i got my CDP-1802s so that i can build the COSMAC Elf...
> now i just need the RAM that the schematics have....i believe that it is 2
> 256x4 RAM chips...if anyone has these or can let me know where i can find
> them could you please let me know
>
> thanks,
> Robert Cobbins
>

Are you going for an authentic recreation, or
would a functional substitution be adequate?
Given how expensive and scarce 1Kx4 2114s
are, 256x4s ought to be even moreso.

There are inexpensive 8-bit wide SRAMs
available with anything from 2Kx8 to
128Kx8, which will do the job nicely in 1 chip.

One tricky thing is that the 1802 multiplexes
its address output in 2 x 8 bit parts,
if I read the data sheet correctly. This means
you would connect only A0...A7 of the available
address pins from the SRAM to the 1802 and
ground the remaining address inputs. You'll
"waste" all but 256 bytes but then again, memory
is cheap. At least the silicon kind. :)

You can demux/latch too, if you really want to
toggle in more than 256 bytes! =:-O Aiiiiieeee!!!
Received on Wed Apr 18 2001 - 03:03:35 BST